JTM45 with EL34's, OT, choke questions

Discussion in 'Shock Brother's DIY Amps' started by Jason McG, Aug 1, 2020 at 1:39 PM.

  1. Jason McG

    Jason McG TDPRI Member

    Apr 8, 2020
    Calgary Canada
    I have a Bassman/JTM45 sort of thing in the works. Was going to be a 5F6A, but wanted to do a head and cab, so that's where I decided to use a JTM45 chassis and layout. I have my 4x10 open back cab done and ready for tweed. Should look like a JTM45 in Bassman's clothing.
    843FFA73-5E66-4B72-8DDC-BACA1C3F198C.jpeg 5EE51F43-B529-44DE-913E-071297720566.jpeg
    I am spec'ing out transformers, with the intent to run EL34's, and am looking for advice, on whether the Hammond 1750N is a suitable OT. I noticed the EL34 based JTM45's usually run an OT with 3.4k primary, and the Hammond has 3.2k. I assume that difference is not significant to the safe running of the amp, and if anything, it would just break up a bit sooner - am I off base here?

    Also for the choke, was planning on the Hammond 194F, which is 5HY 120mA 115 ohm, and looking at EL34 kits like mojotone and stewmac, the chokes they spec are 3HY 120mA 106 ohm, and 3.5HY 100ma 100 ohm. Are these close enough in spec to be interchangeable?

    Reason for the Hammond choice is being in Canada, plus have used Hammond with great satisfaction on my tweed champ and deluxe builds.

    Thanks for any help,
    NSB_Chris and Wally like this.
  2. dan40

    dan40 Tele-Afflicted

    Aug 19, 2015
    Richmond Va
    All of the items you listed are so close in specs that you won't have any issue with any of them and they will all be interchangeable without any worries. Good luck with your build and keep posting pics of the progress.
    Jason McG likes this.
  3. Lowerleftcoast

    Lowerleftcoast Tele-Afflicted

    Dec 30, 2019
    Agree with dan40.
    Chances are you will not tell any difference. With voltages being equal, the 3k4 would probably break up sooner than the 3k2. They are too close for a noticeable difference is my bet.
    Jason McG and dan40 like this.
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